The invention relates generally to level measurements, and more particularly to an improved inclination gauge providing visual, audio and vibration indicators.
For many years it has been known to use what is commonly called a carpenter's level to measure vertical and horizontal angles. Such devices generally employ an accurate tube partially filled with a liquid so as to provide an air bubble therein. The carpenter's level is used by placing the frame of the level on the object to be measured, and then adjustments are made in the angular orientation of the level until the bubble in the accurate tube centers, usually between two indicia placed on the tube, thereby indicating either a horizontal or vertical angle. Furthermore, indicators of angles either greater or less than the desired angle are indicated by observing which side of the indicia the bubble rests when not centered.
This type of prior device requires the visual judgment of the user to determine when the air bubble is centered. This is often difficult especially when the angle being measured requires an unusual attitude of the level, thereby placing the air bubble at an inconvenient viewing angle or distance. There are occasions when a job requiring leveling becomes extremely dangerous, such as upper floors of a high-rise, on roof tops, ladders, etc. In many of these jobs, even when working at extreme heights, the worker must lean outward from a safe position to reach a required location where a reference line must be inscribed, and at this location may find himself stretching even further outward to position his line of vision as directly in front of the leveling bubble as possible in order to obtain as correct a reading as possible. In this stretched out position he becomes vulnerable to a fall or an inaccurate reading or inscribed line.
There are many other problems associated with reading common bubble levels, namely, use in unlit areas, reflection on eyeglasses of the user, over the head leveling requirements where the bubble cannot be clearly seen, etc.
U.S. Pat. No. 4,077,132 issued to inventor Kent E. Erickson teaches a level indicator providing a display of gravity related attitude comprising a capacitive gravimeter pickup assembly, the complementary capacitor pair of which are alternately switched, on an equal-time basis, into an R.C. oscillator circuit. Concurrently, each oscillator pulse train is switched, respectively, into the up and down mode of reversible counting means to yield a net oscillator frequency difference directly, digitally indicative of the degree of departure from a gravity referenced level condition. A digital display is included.
U.S. Pat. No. 4,079,521 issued to inventor Theodore Uhorezak teaches an electrically actuated level having a housing with a straight edge for providing a visual signal to indicate either a horizontal or vertical orientation of the straight edge or for indicating a deviation therefrom and the direction of that deviation. The level includes a 90.degree. rotatable sensing device mounted centrally in the housing. The sensing device includes a power switch. Three LED are provided to indicate a desired horizontal or vertical orientation and off desired orientation. The switch comprises a pair of glass envelopes with an electrode for each of the LEDs and a ground electrode. A conductive liquid (mercury) provides contact between the ground electrode and one of the light electrodes.
U.S. Pat. No. 4,152,839 issued to inventor Edward L. McDonald teaches advice similar to the Uhorezak device.
U.S. Pat. No. 4,167,818 issued to inventor Robert Cantarella et al teaches the use of a conductive liquid type potentiometer the output voltage of which is conditioned to produce a digital display indicating a null when the desired position is reached. A conventional spirit level is used to verify the digital readout.
U.S. Pat. No. 4,182,046 issued to inventor Roger D. Ludlow et al teaches an electrically responsive level. The level relies on a bubble-within-a-vial type inclination sensor. The level condition is provided by audio and visual light indicators.
U.S. Pat. No. 4,244,117 issued to inventor Robert Cantarella et al teaches a level with a gravity sensing potentiometer associated with an electrical balance circuit generally as discussed above. The potentiometer includes electrodes and a conductive liquid. A digital display is provided.
U.S. Pat. No. 4,253,242 issued to inventor Terrance M. McInerney teaches a digital angle indicator comprising a rotatable mounted gravity responsive opaque rotor having transparent slots therein for selectively passing light from light sources to light detectors. The detectors activate visual indicators which display angles of attainment and values greater or lesser than the angles of attainment.
Obviously, these above mentioned devices operate at least as good as the age old spirit type level, with improved indication means.
The obvious drawbacks of these devices are that they are fragile and extremely susceptible to damage, breakage or inaccuracies when subjected to the normal every day use of a typical construction worker. The batteries for powering the electronics and indicators will be susceptible to a short life unless the power was turned off after each use. In most instances, the power would be left on as a convenience for occasional continual use during a work day. The liquid used for the potentiometer, generally mercury, would continue to slosh about in the tube for a period of time and due to the general size and position of the electrodes would have to be completely at rest to get an accurate indication.
Some of the prior art devices employ mechanical bearings which wear and the width of light emitting slots and LEDs size provide a built in accumulative error in angle indication.
Some of the prior art devices utilize switches to preset the desired angle inaccurate settings or the operator forgetting to set these switches when the level is used could cause unknown errors in angle indication.
Some of the prior art devices cannot be inverted which some users require.
Some of the prior art devices require spirit level in combination to determine accuracy of the electronic portion.
In general the prior art devices are slow to accurately indicate an angle.
The present invention avoids the disadvantages generally found in previously available instruments of this type and provides a rugged, compact, fast angle indicating device which requires little power for its operation, provides automatic power shut off when not in use, has a high degree of accuracy and provides a visual, audio and vibratory angle indication.